I have a script giving me error 403 Forbidden error, it\'s just a copy of another script but the difference in this is that both use another mysql class to acce
Check the permissions and also ownership of the file. Generally, 403 means that the web server doesn't have the rights to read the file and therefore can't continue the request. The permissions may be set correctly, however the file might be owned by another account on the server - an account that isn't part of the same group as the account which is running the server.
For instance, I believe* Apache is ran by default under the httpd user account, which is part of the httpd group. However, the FTP user you're logging in as (for instance ftpuser) might not be part of the httpd group. So, in copying the file you've created it under a different user account and Apache won't get execute access with 644.
* it's been a while since I've used apache, but it's similar under nginx.